Wearable devices such as smart watches, fitness trackers, smart glass etc., are gaining in popularity in the marketplace today. Consumers who want to lose weight and/or improve their health can benefit from these wearable devices by being aware of the level of their physical activity on a day-by-day, week-by week basis, etc. Such awareness helps motivate the customer to use the stairs or walk the dog an extra lap around the block. These Wearable devices are smart and accurate. Besides measuring how much one walks, they provide good insight into lifestyle habits such as sleep, calorie consumption, heart rate, blood pressure, skin temperature, perspiration, etc.
Wearable devices operate of a rechargeable battery. These batteries are typically recharged via a Universal Serial Bus (USB) Interface connectors or via wireless power. Wireless power enables a slimmer construction and waterproof capability for the Wearable device besides being a more convenient means for recharging for the consumer. However, the wireless power receiver circuitry is typically included in the back of the watch or that portion of the fitness tracker which makes contact with the skin. This back part of the Wearable device is prime real estate as this is where the sensors to measure heart rate, skin temperature, etc., are included. When included in this valuable space, the wireless power circuitry reduces the space that is available for the sensors. Their proximity may trigger incorrect operation and false alarms in the sensors and/or in the operation of the wireless power circuitry.
Wearables are built in different shapes and sizes. Some Wearables such as the smart watches have a flat surface area such as in the back of the watch while other Wearables such as the fitness trackers, hearing-aids, smart glasses, etc., have very little flat surface area. When the flat surface area is limited, the wireless power transmit circuitry in the charger and the wireless power receiver circuitry in the portable device are usually rotationally misaligned when the portable device is placed on the charger. Even when there is sufficient flat surface area, the device may be placed on the charger in a fashion wherein there is significant rotational misalignment between the wireless power circuitries in the portable device and the charger. For example, instead of being placed flat on its back, a smartwatch may be placed vertically on its straps on the charger. Existing wireless charging technologies and solutions can wirelessly charge the device when the level of rotational misalignment is typically less than 30 degrees. When the level of rotational misalignment exceeds this level, the charger is unable to wirelessly charge the portable device.
Therefore, there is an unmet need for a wireless power system that may occupy very little to no space in this vital sensor area of the device, which by design can be physically apart and hence have little interaction with the sensors and other critical circuitry in the device and which can wirelessly charge the portable device when the device is placed on the charger irrespective of the level of rotational misalignment between the wireless charging circuitry in the device and charger.